Method and casing for excavating a borehole

Abstract

A soft excavator (10, 90, 110, 130) is disclosed which utilizes a jet of high velocity fluid flow such as air or water flow, preferably supersonic, through a nozzle (48, 92, 112) to excavate a material, such as the ground. A second passage for air flow is provided which is directed by an evacuator skirt (52, 102) in a direction along the excavator generally opposite the direction of discharge of the high velocity excavating flow to entrain the material excavated for disposal.

We claim: 
     
       1. A casing for use in excavation of a borehole by an apparatus directing a high velocity fluid against the material to be excavated, the borehole having a predetermined diameter, comprising: a tubular portion of diameter to be moved within the borehole as it is excavated to maintain the diameter of the borehole, the tubular portion moved into the borehole as the borehole is excavated by the apparatus;   a seal portion secured at an end of said tubular portion for passage of the apparatus for excavation within the tubular portion to direct the high velocity fluid at the excavation site, the apparatus moving relative to the casing as excavation is undertaken, a seal provided in said seal portion to seal against said apparatus as the apparatus moves relative to the casing during excavation; and   a discharge portion to discharge material excavated by said apparatus from the site of excavation along the interior of the tubular portion for disposal.   
     
     
       2. The casing of claim 1 further having a handle mounted on the casing for an operator to manipulate the casing within the borehole being excavated. 
     
     
       3. The casing of claim 1 wherein the tubular portion has a lower end extending into the borehole, the lower end having cutting teeth for assisting in excavation of material in the borehole. 
     
     
       4. The casing of claim 1, wherein the discharge portion includes a downwardly directed elbow to discharge material downwardly to avoid interference with an operator using the apparatus and casing. 
     
     
       5. The casing of claim 1 wherein the tubular portion and discharge portion are made of PVC plastic. 
     
     
       6. The casing of claim 1 wherein the tubular portion and discharge portion are made up of fiberglass. 
     
     
       7. The casing of claim 1 wherein the tubular portion is a straight section of pipe, the seal portion is a pipe tee and the discharge portion is a pipe elbow. 
     
     
       8. The casing of claim 1 wherein the tubular portion of the casing is left in the borehole to form a liner after the excavation is completed, the seal portion and discharge portion removable from the tubular portion after excavation is completed. 
     
     
       9. The casing of claim 1 further comprising a step mounted on the casing for an operator to apply weight to force the casing into the borehole. 
     
     
       10. A casing for use in excavation of a borehole by an apparatus directing a high velocity fluid against a material to be excavated, the borehole having a predetermined diameter, comprising: a tubular portion of diameter to be moved within the borehole as it is excavated to maintain the diameter of the borehole;   a seal portion secured at an end of said tubular portion for passage of the apparatus for excavation within the tubular portion to direct the high velocity fluid at the excavation site, a seal provided in said seal portion to seal against said apparatus;   a discharge portion to discharge material excavated by said apparatus from the site of said excavation along the interior of the tubular portion for disposal; and   a handle for grasping by an operator to manipulate the casing within the borehole.   
     
     
       11. The casing of claim 10 wherein the seal portion and discharge portion are removable from the tubular portion, the tubular portion remaining in the borehole to form a liner. 
     
     
       12. A method of excavating a borehole with an apparatus directing a high velocity fluid against the material to be excavated, the borehole having a predetermined diameter, comprising the steps of: inserting the apparatus through a seal portion of a casing, the casing further having a tubular portion of diameter corresponding to the predetermined diameter of the borehole;   excavating the borehole with the apparatus while pushing the tubular portion of the casing into the borehole to maintain the diameter of the borehole;   discharging the material excavated by the apparatus from the site of excavation along the interior of the tubular portion to a discharge portion of the casing for discharge.